Mitsui Mining & Smelting Co. Ltd.

1-11-1 Osaki, Shinagawa-ku
Tokyo, 141-8584
Telephone: (+81 3) 5437-8000
Web site:

Public Company
1950 as Kamioka Mining & Smelting Co. Ltd.
Employees: 12,276
Sales: ¥519.21 billion ($4.68 billion) (2017)
Stock Exchanges: Tokyo
Ticker Symbol: 5706
NAICS: 212230 Copper, Nickel, Lead, and Zinc Mining; 331410 Nonferrous Metal (except Aluminum) Smelting and Refining; 331523 Nonferrous Metal Die-Casting Foundries; 333511 Industrial Mold Manufacturing

Mitsui Mining & Smelting Co. Ltd. (MMS), also known as Mitsui Kinzoku, is one of the world's largest producers of zinc and engineered materials such as ultrathin copper foil. It smelts, refines, and fabricates nonferrous metals that are used in high-tech industries, and produces components and die-cast products that are used in a variety of applications including automobiles and home appliances. The company's operations are organized into four business segments: Engineered Materials, Metals, Automotive Parts and Components, and Affiliates Coordination.


MMS was created as Kamioka Mining & Smelting Co. Ltd. in 1950, when the Mitsui Mining Company was forced to dissolve by the Allied occupation forces in Japan. Mitsui Mining was one of the oldest and most important of the many affiliates of the Mitsui zaibatsu (conglomerate), its large coal mines having first been acquired by the parent company in 1889. Mining of coal and nonferrous metals quickly became one of the three pillars of the vast Mitsui empire, along with banking and trade; and Mitsui Mining, which was founded as a separate company in 1892, continued for many years to occupy a central place in Mitsui's strategy. Able at that time to exploit the labor of poorly paid women and children, prison convicts, and often prisoners of war, Mitsui Mining was not only extremely profitable but also provided the steady income that allowed the zaibatsu to diversify into other, riskier areas. The company's bulwark was the mining of coal from its Miike mines on the island of Kyushu, but it soon acquired a host of zinc, copper, lead, gold, and silver mines around Japan. Its precious metals holdings were especially important as a means of stabilizing income during the often-wild price fluctuations of the industrial metals, the value of gold tending at that time to remain much more stable.


With creativity and productivity, We, MMS Group, will explore products of value to society, and seek an eternal growth of our group.

Mitsui Mining was thus an integral part of Japan's war machine as well as remaining one of the key firms in the Mitsui group. As a result, when General Douglas MacArthur and the Allied occupation forces attempted to dismantle the monopolistic power of Japan's great zaibatsu at the conclusion of the war, Mitsui Mining was one of the dozen or so Mitsui affiliates singled out for special attention. The aim of the occupiers was both to weaken Japan's ability to wage war and to encourage Western-style democracy by fostering competition in each industry.

Mitsui Mining was felt to be doubly objectionable, having provided raw materials for the war effort and also ranking as Japan's leading producer of coal and nonferrous metals. Therefore, occupation authorities ordered the company to be divided into two parts. The Mitsui Mining Company was instructed to continue its coal production, based at the Miike mines, while the Kamioka Mining & Smelting Co. Ltd. was established to handle all other mining activities. In 1950 the two companies were legally separated and Mitsui Mining became an independent corporation in the new Japanese economy, one that was ostensibly free of the concentrated power formerly wielded by the zaibatsu.


With the Allied disruption of the zaibatsu, the Mitsui family and the other leading Japanese industrialist families largely lost control of their conglomerates. The Allied reorganization of Japanese business groups was short-lived, however, with the anxiety of the United States over the potential spread of communism in Asia quickly overshadowing its concern with democracy in Japan. The United States wanted a strong, dependable Japan as its sentinel in the Far East, and it was evident that the tradition of cooperation and planning embodied in the zaibatsu concept was essential to Japan's past and future economic health, however poorly it satisfied Western ideas of free competition in the marketplace or at the ballot box. Serious anti-zaibatsu policies were dropped by the time of Kamioka Mining & Smelting's creation, leaving the essential fabric of Japanese economic life unchanged and making it possible for the Mitsui companies to slowly reestablish their former network. One of the first manifestations of the reemergence of zaibatsu was in 1952, when Kamioka Mining & Smelting Co. Ltd. was renamed Mitsui Mining & Smelting Co. Ltd.

The new MMS had taken over from its parent company the largest and highest-quality zinc mine in Japan, and probably in the entire Eastern Hemisphere. The company's Kamioka works in Toyama Prefecture on the island of Honshu produced half of Japan's zinc during the early 1950s and continued to dominate the Japanese zinc market well into 2000. Another early success of MMS was in lead, of which it continued to provide a third of Japan's requirements, down since the war but soon to increase again. The example of lead was typical in MMS's history in particular and in Japan's in general: in great demand during the war for bullet manufacturing, lead's value dropped practically to nothing in the chaotic, severely depressed postwar economy.

However, the phenomenal gains made by the Japanese economy during the next few decades greatly expanded the number of peacetime uses for lead, chief among them the manufacture of batteries for automobiles and other end products. As Japan's auto industry slowly developed after the war, the demand for MMS's lead grew proportionately, fueled also by use of the metal in electric-wire sheathing and as a bearing material. MMS created a thriving business in lead by melting its bullets into batteries. A similar evolution could be traced in the example of precious metals, whose value as industrial catalysts and compounds grew tremendously after the war. MMS's gold and silver mines, although never large by world standards, thus continued to justify the expense of deeper exploration.


Kamioka Mining & Smelting Co. Ltd. is created.
Kamioka Mining & Smelting is renamed Mitsui Mining & Smelting Co. Ltd. (MMS).
Investigators determine that cadmium pollution from the Kamioka mines is causing a degenerative bone disease known as itai-itai among local residents.
Mitsui Copper Foil (Hong Kong) Co. Ltd. is created.
MMS teams up with Nippon Mining & Metals Co. Ltd. to create Pan Pacific Copper Co. Ltd.
The company shutters its mining operations at the Kamioka Mine.
The Sumitomo Metal Mining Co. and MMS form MS Zinc Co. Ltd.
The company begins settlement discussions to address a 1971 order by the Toyama District Court that MMS pay damages to itai-itai victims or their families.
MMS agrees to pay a lump sum of ¥600,000 to 500 to 600 victims of cadmium poisoning.
The company announces that it will increase its production of ultrathin copper foil to meet surging demand from smartphone manufacturers.

The tremendous expansion of the Japanese economy during the 1960s resulted in a proportionate surge in sales at MMS. The burgeoning Japanese auto industry bought not only lead for its batteries from MMS but also an increasing number of die-cast parts such as door latches. The manufacturing of such finished products marked a new era at MMS, which, like the rest of Japanese industry, began a slow shift from basic to value-added products in the face of increased price competition from other Asian industrial nations. Thus, just as Japan evolved from world domination in steel to that of shipbuilding and then to electronics, MMS began seeking ways to use its metal resources and experience in the manufacture of higher value-added products.

In 1981, for example, the company formed a joint venture in Tokyo with Mallinckrodt Incorporated to manufacture catalysts for the food processing, petrochemical, and synthetic fiber industries. Many catalysts made use of precious metals such as gold and platinum, which brought a greater return to refiners such as MMS when sold in the form of complex industrial products rather than merely as ore. MMS continued its evolution from raw-material producer to manufacturer of material-based products, and the company clearly intended to proceed further in that direction during the late 1980s.


The Japanese postwar economic recovery resulted in a number of unwanted additions to Japanese life, including environmental pollution. MMS's role as a smelter of metals led it into several entanglements in this area, the most notorious of which came to a head in 1968. For years the population living along the Jinzu River downstream from MMS's big Kamioka zinc mines had suffered from a variety of disorders, which the residents attributed to Kamioka's contaminated effluent. Japanese companies were traditionally uninterested in addressing such problems, and it was not until 1968 that investigators determined that cadmium pollution from the mines was causing a degenerative bone disease known as itai-itai, or “ouch-ouch,” among local residents. A lawsuit was filed by 28 citizens on behalf of some 500 alleged victims of fatal or crippling itai-itai disease. In 1971, for the first time in Japanese history, the corporation was found guilty and ordered to pay damages that in the aggregate amounted to approximately one year's net income. Despite the legal judgment for the victims, no settlement would be reached for more than 40 years.

MMS looked to the electronics field for a significant portion of its growth during the 1990s and beyond. Products developed during the late 1980s and early 1990s were grouped under a new materials division. These included products made from high-purity metals such as tantalum and niobium, copper foil for laminates, and sputtering targets used in the application of very thin coats of metal. In 1990 the company adopted a new corporate logo and became known in Japan as Mitsui Kinzoku.

During the mid-1990s the company shuttered its lead refining business as part of a restructuring plan designed to shore up profits and focus on the race to develop more complex materials for the fast-growing high-tech components market. It established two new subsidiaries in 1995: Mitsui Siam Components Co. Ltd. and Mitsui-Huayang Automotive Components Co. Ltd. Mitsui Copper Foil (Hong Kong) Co. Ltd. was created in 1998. The company headquarters were moved to Osaki, Shinagawa-ku, Tokyo, the following year.


During the early years of the new millennium, MMS faced increased competition and falling demand for zinc and electronics-related materials. In response to industry conditions, the company cut costs, revamped operations, and made several key joint ventures. In 2000 it teamed up with Nippon Mining & Metals Co. Ltd. to create Pan Pacific Copper Co. Ltd., which oversaw the copper activities of both companies. Two years later, it partnered with the Sumitomo Metal Mining Co. to form MS Zinc Co. Ltd. In 2001 Mitsui Copper Foil (Guangdong) Co. Ltd. was created to produce electrodeposited copper foil in China. That same year the company shuttered its mining operations at the Kamioka Mine in an attempt to cut costs and improve profitability. In 2002 Mitsui Components Guangdong Co. Ltd. was established to produce automotive parts in China. It also acquired Ohi Seisakusho Co. Ltd. in 2003 to bolster its automotive components business.

In March 2006 the company began zinc ore production at the Pallca Mine in Peru. It also continued to expand production of automotive components, opening new offices in Thailand and China. An automotive components subsidiary was also established in India in 2005. During this time period MMS struggled to sustain consistent sales growth and profitability. In 2007 the company experienced losses in its semiconductor mounting materials business that included Tape Automated Bonding tape and Chip On Film tape products. In addition, the price of zinc was lower than the company anticipated. Its net income fell dramatically that year, from ¥31.3 billion recorded in the previous year to ¥7.8 billion in the fiscal year ending March 31, 2008.

In 2009 MMS announced that its fiscal year sales of ¥427.2 billion represented a 28.3 percent decline in sales from the previous year. In response, the company reduced its workforce by more than 4,000 employees and restructured operations in an attempt to increase revenues and shore up profits. MMS management, led by President and CEO Yoshihiko Takebayashi, was concerned about what Takebayashi called “an unprecedentedly severe operating environment” caused by global economic crises that resulted in dramatic reductions in demand for automobiles and electronic appliances. At the start of 2010 Sadao Senda succeeded Takebayashi as president of MMS. Reported sales for the year fell once again to ¥392.4 billion, a decline of 8.2 percent. Senda observed in that year's annual report that although the company's performance in fiscal 2009 was negatively impacted by general instability in the Japanese economy, higher exports and economic stimulus policies pointed the way to a modest recovery. The report also noted that after a two-year hiatus, the company once again paid shareholders a dividend of ¥3 per share.


In 2012 and 2013 MMS continued to pursue sustainable growth. Slow economic recovery in the United States and slowed-down growth in emerging markets combined with domestic challenges on the economic front to reduce annual sales during both years. A bright spot for the company was high demand for its ultrathin copper foil, which was used in smartphones. Demand also increased in 2013 for materials needed to produce lithium manganese oxide batteries, which were used in electric vehicles. As fiscal 2013 drew to a close, the company announced yet another reorganization, this time into three sectors: engineered materials; metals; and the Mitsui Kinzoku ACT Corporation, which would focus on automotive parts and components.

The year 2013 also marked the resolution of the cadmium poisoning judgment against MMS. The fight began in 1971, when the company was ordered to pay damages to survivors and their families in what was known as the itai-itai case. Negotiations with survivors began in 2009, and in December 2013 the company finally agreed to pay a lump sum of ¥600,000 to hundreds of people who suffered kidney damage related to the pollution of the Jinzu River that began during the early years of the 20th century. According to the Japan Times, the company president Senda apologized “from the bottom of my heart,” pledging to “continue working for the sufferers and make efforts to prevent pollution.”


Fiscal 2014 saw an increase in sales for the first time since 2011. Although a fall in crude oil prices worldwide reduced demand for hybrid cars, thus softening the market for the materials used to produce electric vehicle batteries, continued high levels of smartphone production increased demand for the company's copper foil. Additionally, as the North American auto industry continued its post-recession recovery, overseas demand rose for auto parts including the company's door locks, even as domestic sales declined. Its annual sales in 2015 increased to ¥473.3 billion, before dipping once again to ¥450.6 billion in 2016.

In April 2016 Keiji Nishida replaced Senda as MMS president. In his report to shareholders that year, Nishida described the outlook on the global economy as “shrouded in uncertainty,” despite moderate growth and continued recovery in the United States and elsewhere. The following year, with annual sales of ¥436.3 billion for fiscal 2017, he expressed concerns about “the impact of Brexit,” as well as the expansion of protectionist economic policies throughout Europe and in the United States. Even so, MMS was feeling optimistic about its future in two high-growth markets. As the leading producer of ultrathin copper foil, with a market share of more than 90 percent, MMS was positioning itself to boost its monthly production capacity by almost 50 percent by the fourth quarter of 2018 to meet increased demand from smartphone manufacturers. There was also optimism about MMS's contribution to next-generation, solid-state batteries for electric vehicles. As a leading supplier of lithium manganese oxide and nickel-lithium, both needed for battery production, the company was also working on a lithium sulfide-based electrolyte that it hoped to bring to market by 2020. The electrolyte was expected to be used to make batteries that are safer, longer-lasting, and more quickly charged than current lithium-ion batteries.

Jonathan Martin
Updated, Christina M. Stansell; Pamela Willwerth Aue


Automotive Components Technology India Private Limited; GECOM Corp.; Mitsui Components Europe Ltd.; Mitsui Copper Foil (Hong Kong) Co. Ltd.; Mitsui Copper Foil (Malaysia) Sdn. Bhd.; Mitsui Copper Foil (Suzhou) Co. Ltd.; Mitsui Electronic Materials Co. Ltd.; Mitsui Kinzoku ACT Mexicana, S.A. de C.V.; Mitsui Kinzoku ACT (Shanghai) Management Co. Ltd.; Mitsui Kinzoku Catalyst Zhuhai Co. Ltd.; Mitsui Kinzoku Catalysts America, Inc.; Mitsui Kinzoku Catalysts (Thailand) Co. Ltd.; Mitsui Kinzoku Catalysts Vietnam Co. Ltd.; Mitsui Kinzoku Korea Co. Ltd.; Mitsui Kinzoku Trading Co. Ltd.; Mitsui Mining & Smelting Co. Ltd. Sucural del Peru; Mitsui Siam Components Co. Ltd.; Pan Pacific Copper Exploration Chile Ltda.; Pan Pacific Copper Exploration Peru S.A.C.; Pt. Mitsui Kinzoku ACT Indonesia; Pt. Mitsui Kinzoku Catalysts Jakarta; Shanghai Mitsui Xin Yun Precious and Rare Metal Recycle Co. Ltd.; Taiwan Copper Foil Co. Ltd.


Affiliates Coordination; Automotive Parts and Components; Engineered Materials; Metals.


Mitsubishi Materials Corporation; Strattec Security Corporation; Sumitomo Metal Mining Co., Ltd.; Toho Zinc Co., Ltd.; Trevali Mining Corporation.


“Itai-itai Victims Settle with Mitsui Mining.” Japan Times (Tokyo), December 17, 2013.

“Mitsui Kinzoku Seen Bracing for FY08 Pretax Loss.” Asia Pulse, January 8, 2009.

“Mitsui Mining & Smelting to Cut 4 Thousand Workers/Late this September.” Japan Metal Daily, January 21, 2009.

“Mitsui Mining Seen Nearly Doubling First-Half Profit.” Asia. , October 17, 2017. Accessed August 27, 2018. .

“Mitsui Mining, Nippon Mining to Launch Copper Project in Peru.” Kyodo News (Tokyo), November 7, 2007.

Roberts, John G. Mitsui: Three Centuries of Japanese Business. 2nd ed. New York: Weatherhill, 1991.

Watanabe, Chisaki. “Why Mitsui Mining Is Excited for Next-Gen Battery Storage.” Bloomberg, September 21, 2017.